In a medical setting it may be necessary or desirable to transfer fluid to/from a subject for a variety of reasons. For example, a hub connected to a needle or other cannula may be used to draw blood from a vein or to infuse fluid substances i.e. intravenous (IV) therapy. A drip is one type of IV therapy. IV therapy may be used to correct electrolyte imbalances, to deliver medications or nutrition, for blood transfusion or as fluid replacement to correct dehydration. IV therapy can also be used for chemotherapy of cancer patients. Fluid-transferring devices such as syringes may also be attached to a hub that connects a cannula for the addition or removal of fluid to/from a variety of bodily cavities, organs or vessels. For instance, the hub may be part of an entity providing a catheter to drain urine from the bladder or kidney, to remove fluid from an abscess, to extract liquid from joints or cysts, or to administer breathing gases through a tracheal tube. A typical endotracheal tube includes a cuff inflation tube with a hub for attachment of a syringe to enable inflation to seal the trachea and bronchial tree against air leakage and aspiration of fluids. A tracheostomy tube or urinary tract catheter might also use a cuff system with a hub for connection of a syringe or other device to inject fluid to inflate a cup or balloon that holds it in place. However fluid injections using a syringe connected to a needle are one of the most common health care procedures in the world.
When transferring fluids to/from a subject, the hub with its needle, catheter or other cannula inserted in the patient is often left in-situ while the fluid-transferring device may be removed and replaced, e.g. to empty/re-fill a syringe or to change over the IV therapy. Where two medical devices that carry small fluid volumes must be connected, a standard Luer fitting is the most common means of achieving a leak-free junction. One type of Luer fitting, commonly called a “Luer lock/lok”, uses an internally threaded collar surrounding a “Luer slip” friction fit (see below) tapered male tip of a syringe or the like. The projecting tip can be inserted into a corresponding female hub with an external thread and the collar screwed down to lock the connection. Such Luer lock fittings have the advantage of providing a secure connection that can not easily come loose, but two hands are needed to hold the hub while screwing the device in/out. A more rapid form of attachment may be preferred in some circumstances, for example in an emergency situation. Another type of Luer fitting, commonly called a “Luer slip”, simply uses a friction fit between a female hub and corresponding tapered male tip of a device without a threaded collar. A standard friction fit is achieved by a 6% taper. A Luer slip attachment is common for infusing less viscous fluids, such as vaccinations, and transferring fluids where high pressures are not involved, for example when drawing blood.
A problem observed with both Luer lock and Luer slip connections is the risk of injury when detaching the fluid-transferring device from a hub that is still connected to a patient. While a medical practitioner might take care to hold the hub and avoid injury when unscrewing a Luer lock connection, there is a temptation with a Luer slip connection to try to pull the device from the hub e.g. with one hand. However this can easily result in the hub being tugged away from the body and causing tissue damage. Often the device may not be pulled in a straight line with the cannula connected to the hub, but rotated, and this can twist the components. The tape used to hold the hub e.g. IV port in position is often loosened from the skin and its cannula e.g. needle may even be accidentally extracted. When emptying fluid from a body cavity, for example, keeping the needle hub still when detaching the syringe can be essential to avoid diffuse cutting inside the cavity or damage of the cavity wall. In addition there is a risk of unacknowledged contamination of both the hub and the Luer tip (not only the user) when holding the very small hub with the thumb and index fingers while pulling away the male tip, the tip sliding past the user's fingers as it is released.
Moreover tugging with a single hand does not usually apply enough force even to pull the device out of a friction fitting (such as a Luer slip) and, depending on the force used when connecting the Luer slip tip to the hub, the practitioner usually needs to hold or push the hub while also pulling the device so that it becomes detached. Typically the device will be rotated simultaneously while pulling away from the hub. This jerking can result in unwanted extraction of the needle or other component connected to the hub. The connection will often be pressurised by fluid. For example, a cuff connected to a tracheostomy tube, endotracheal tube or urinary catheter often has a tight connection of the male Luer tip with two-handed operation being required to loosen the connection while the sprung piston in the female Luer hub blocks the outflow of fluid (air or liquid) from the cuff.
Ease of disconnection can be a problem not only when detaching a device from a hub connected to a patient but also when it is desired to fill/empty a device such as a syringe via a fluid hub in a quick and convenient manner. For example, when filling a syringe using a needle inserted in a vial, each time that the syringe is removed it requires two hands to firmly grasp the needle hub and the syringe to separate them while the needle remains in the vial. As mentioned above, there is again a risk of contamination as the user grasps the hub and the tip comes into contact with the fingers holding the hub.
Another situation where a user might come into contact with a needle hub is when using a blood collection tube. The blood tubes are evacuated plastic or glass containers sealed with an elastomeric septum that is piercable by a double-ended needle to draw venous blood. Due to the piercing force and pressure differential, a secure connection to the needle assembly is required and therefore a threaded Luer lock connection is normally used rather than a Luer slip. U.S. Pat. No. 5,201,716 proposes an alternative blood specimen collection system that does not require the needle assembly to be grasped and twisted during disconnection. In this system a needle assembly is mounted with an interference fit rather than a threaded connection. A pivotally mounted lever assembly is spring-biased to hold the needle assembly in position, i.e. to provide an additional level of security over the friction fit. If the lever is actuated against its spring bias then there is only an interference fit holding the needle assembly in place. The lever can be pivoted to simultaneously release the spring bias and to apply a forward ejection force to the needle assembly.
In any situation where one hand is holding a needle hub while pulling a device away there is a risk of needlestick injury and contamination. Needle caps frequently being mislaid or forgotten can exacerbate this. This also applies when separating a needle or other contaminated component from a syringe or similar device for disposal purposes, with many needlestick injuries occurring when trying to remove sharps to throw into a bin. Usually the person handling a syringe will try to cover a contaminated needle with a cap after use, before grasping the hub to separate the needle from the syringe barrel for disposal. However, when mounting a needle cap onto the contaminated needle a person will use the large muscle groups in the arms and shoulders that work less precisely and, combined with poor depth of vision, this often results in a needlestick injury to the fingers holding the needle cap. It would be better if a needle hub could be safely released without needing to cap the needle or handle the connection.
There are various fluid transfer procedures in the medical setting that may require a very secure connection between a fluid transfer tip (e.g. provided by a syringe) and a corresponding hub. The hub may be connected to a needle or catheter inserted into an artery, vein, cavity or organ of a patient. In the field of cardiology, angiography and angioplasty procedures may inject fluids (liquid and/or air) into narrow channels at high pressure. Manual syringes and manifold sets are used for percutaneous coronary interventions and coronary diagnostic procedures such as angiography. A cardiac angiographic kit typically comprises a catheter hub for connection, a catheter body of chosen size, length and stiffness, and a tip with a single end-hole to eject fluids. The catheter body is inserted into the coronary vessels, ventricles and/or peripheral vasculature. A syringe may be connected to the catheter hub to inject contrast agents or saline at pressures ranging between 250 and 800 psi, and even up to 1000 or 1200 psi (84 bar). The catheter hub has an external thread to provide a standard Luer lock connection.
Luer lock connectors have become universal, not only for joining syringes to hubs, but also for connecting small-bore medical tubing and hoses for liquids and/or gases. Luer lock connections are commonly used for vascular IV lines but also find use in other medical treatment or diagnostic systems. Tubing and hoses may use a Luer lock connection for cuff inflation systems, feeding tubes, catheters, and hoses for vascular, enteral, respiratory, neuraxial and urethral/urinary systems.
The screw connection of a Luer lock hub is often considered necessary to withstand high pressures. However a syringe, hose or other fluid transfer device must be rotated to connect, and disconnect, its Luer lock collar to/from the hub. This can take time and requires a two-handed operation. Furthermore, when a user grips the hub to unscrew the connection there is a risk of contamination, especially where the hub includes a needle that may carry blood on its shaft. It would improve the efficiency and workflow of medical procedures if a fluid transfer device could be disconnected from a Luer lock hub more easily.
The present invention seeks to address or mitigate the problems outlined above.